Watercraft propelled with tread force

ABSTRACT

A watercraft propelled with tread force includes a buoyant hull. A seat unit is mounted on the hull. A propulsion device is arranged to propel the hull. A manually operated apparatus is arranged to power the propulsion device. The manually operated apparatus is disposed in front of the seat unit and comprises a slide mechanism that includes a pair of pedals slideable with tread force alternately given to each one of the pedals by a rider in the seat unit.

PRIORITY INFORMATION

[0001] This application is based on and claims priority to Japanese Patent Application No. 2001-022818, filed Jan. 31, 2001, the entire contents of which is hereby expressly incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates generally to a watercraft propelled with tread force, and more particularly to an improved watercraft propelled with tread force given linearly by the rider.

[0004] 2. Description of Related Art

[0005] Relatively small watercraft such as, for example, canoes and kayaks draw attention of people who enjoy leisure at the water's edge, who like hydro-sports or who want to exercise. Typically, these watercraft are propelled with paddles or oars. Some of the watercrafts are propelled with tread force given by one or more riders, and these kinds of watercraft have become popular in recent years. For instance, U.S. Pat. Nos. 4,943,251 and 5,217,398 and Japanese Laid-Open Publication No. 7-156880 disclose such watercraft.

[0006] The watercraft disclosed in these patents and publication employ rotary pedal-type drive systems. Because the systems need voluminous space for rotations of pedals, the watercraft have cumbersome shapes and sizes. Particularly, the length between the top and bottom positions of the pedals is one of primary factors that makes the watercraft large because such a watercraft typically has a hull elongated fore to aft. Accordingly, the conventional watercraft are relatively bulky and make the carriage or storage thereof difficult.

SUMMARY OF THE INVENTION

[0007] A need therefore exists for an improved watercraft propelled with tread force that can be compact enough particularly in height for carriage or storage.

[0008] In accordance with one aspect of the present invention, a watercraft comprises a buoyant hull. A seat unit is mounted on the hull. A propulsion device is arranged to propel the hull. A manually operated apparatus is arranged to power the propulsion device. The manually operated apparatus is disposed in front of the seat unit and comprises a slide mechanism including a pair of pedals slideable with tread force alternately given to each one of the pedals by a rider in the seat unit.

[0009] In accordance with another aspect of the present invention, a watercraft comprises a hull elongated along a center plane extending fore to aft perpendicularly. A propulsion shaft is journaled for rotation in the rear of the hull and extends generally on the center plane. A propeller is disposed at the end of the propulsion shaft. A manual drive unit is disposed within the hull to convert tread force linearly given by a rider to rotational force that rotates the propulsion shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] These and other features, aspects and advantages of the present invention will now be described with reference to the drawings of a preferred embodiment, which embodiment is intended to illustrate and not to limit the present invention. The drawings comprise eleven figures.

[0011]FIG. 1 is a schematic top plan view of a watercraft configured in accordance with a preferred embodiment of the present invention.

[0012]FIG. 2 is a schematic side elevational view of the watercraft shown in FIG. 1.

[0013]FIG. 3 is a schematic top plan view showing a manual drive unit (or manually operated apparatus) of the watercraft.

[0014]FIG. 4 is a schematic side elevational view of the manual drive unit showin in FIG. 3.

[0015]FIG. 5 is an enlarged side elevational view of a transmission included in the manual drive unit shown in FIG. 3.

[0016]FIG. 6 is a schematic illustration of a power assist unit of the watercraft connected with the transmission shown in FIG. 5.

[0017]FIG. 7 is a partial top plan view of the watercraft showing retractable sponsons linked with a hull of the watercraft. The sponsons are placed in a fully expanded position.

[0018]FIG. 8 is a sectional rear view taken along the line 8-8 of FIG. 7. The sponsons are placed in a fully retracted position.

[0019]FIG. 9 is a sectional rear view taken along the line 8-8 of FIG. 7, with the sponsons in a fully extended position.

[0020]FIG. 10 is a schematic sectional view of a modification of the watercraft shown in FIG. 1.

[0021]FIG. 11 is a schematic sectional view of another modification of the watercraft shown in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION

[0022] With primary reference to FIGS. 1 and 2, an overall construction of a watercraft 30 configured in accordance with certain features, aspects and advantages of the present invention is set forth below.

[0023] In the illustrated arrangement, the watercraft 30 comprises a buoyant hull 32 that is elongated along a center plane CP extending fore to aft and generally has a symmetrical configuration relative to the center plane CP. The hull 32 tapers toward a forward end and bulges outward toward a rear end as shown in FIG. 1. The hull 32 also has generally a inversed trianglar shape toward the bottom. The hull 32 is generally formed with an upper hull section or deck 32 a and a lower hull section 32 b both preferably made of, for example, a molded fiberglass reinforced resin or a sheet molding compound. Both the hull sections 32 a, 32 b are coupled and glued together by bonding agents. A gunwale 34, illustrated in greater detail in FIGS. 8 and 9 covers an intersection of the hull sections 32 a, 32 b.

[0024] Forward and center portions of the upper hull section 32 a preferably are recessed toward the lower hull section 32 b to define a relatively large recessed space 36. The top surface line 37 of the upper hull section 32 a is generally horizontal when the watercraft 30 is floating freely in water, as shown in FIG. 2.

[0025] Each rear portion of the upper hull section 32 a and the lower hull section 32 b together define a cavity that is available for accommodating tools or belongings of the rider through an opening formed at the upper hull section 32 a. A hatch 38 preferably covers the opening. The opening also allows the rider to inspect inside of the hull 32. Optionally, an additional opening can be formed at the lower hull section 32 b to allow a rider to inspect a propeller 40 disposed under the openings through the upper and lower openings. In this latter arrangement, the portion of the cavity, which has the openings, is not available for storage and preferably is divided with partitions from other portions so that water cannot enter inside of the bull 32. As used in this description, the terms “rear,” “rearward” and “rearwardly” mean at or to the side where the propeller 40 is located unless indicated otherwise or otherwise readily apparent from the context use. The terms “front,” “forward” and “forwardly” mean at or to the opposite side of the rear side.

[0026] A pair of retractable sponsons 44 are linked with a rear portion of the hull 32. The sponsons 44 and a linkage mechanism connecting the sponsons 44 to the hull 32 are described in greater detail below.

[0027] A seat unit 46 preferably is mounted on the upper hull section 32 a. Preferably, the seat unit 46 is disposed generally at a center position of the hull 32 fore to aft and on the center plane CP. The seat unit 46 comprises a seat member 48 and a backrest 50 both preferably made of, for example, a plastic material. Both the seat member 48 and the backrest 50 preferably are coupled together by, for example, metallic members. One of the seat member 48 and the backrest 50 or both of them are affixed to the bottom or inner lateral sides of the upper hull section 32 a by proper fasteners such as, for example, bolts and nuts so as to be within the sunk-in space 36. Otherwise, the seat member 48 and the backrest 50 can be separately affixed to the bottom and/or inner lateral sides of the upper hull sections 32 a.

[0028] The location of the seat member 48 preferably is adjustable between a fully forward position and a fully rearward position with a conventional mechanism which, for example, car seats usually employ. The backrest 50 preferably is reclineable to change angles thereof. The backrest 50 can be flat, i.e., in a fully reclined position such that the rider can rest in a horizontal position while the watercraft 30 stands still. A top end of the backrest 50 preferably is positioned generally lower than the top surface line 37 of the hull.

[0029] With continued reference to FIGS. 1 and 2 and additional reference to FIGS. 3-5, a manual drive unit or manually operated apparatus 54 are described below.

[0030] The manual drive unit 54 is located in front of the seat unit 46. The manual drive unit 54 generally comprises a slide mechanism 56, a converting mechanism 58 and a flexible transmitter 60 that couples the slide mechanism 56 with the converting mechanism 58. The mechanisms 56, 58 and the flexible transmitter 60 are generally on the center plane CP and extend along the center plane CP. Also, the mechanisms 56, 58 and the flexible transmitter 60 are placed within the recessed space 36.

[0031] The slide mechanism 56 preferably includes front and rear frame members 64, 66 spaced apart from each other fore to aft and affixed to the upper hull section 32 a by fasteners such as, for example, bolts and nuts. Preferably, the frame members 64, 66 generally are rectangular metallic plates and extend generally vertically and normal to the center plane CP such that each vertical center line lies on the center plane CP.

[0032] Four guide rails 68, preferably are made of a metal material, generally horizontally extend between the front and rear frame members 64, 66. The ends of the guide rails 68 are affixed to the front frame member 64 and the rear frame member 66 by fasteners such as, for example, bolts and nuts. Two of the guide rails 68 lie on the port side relative to the center plane CP above or below one another and extend generally in parallel to each other. The other two of the guide rails 68 lie on the starboard side relative the center plane CP above or below one another and extend generally in parallel to each other. Both the upper guide rails 68 extend generally in parallel to each other, while the lower guide rails 68 extend generally in parallel to each other. The frame member and guide rail assembly defines a framework which extends generally horizontally fore to aft and symmetrically relative to the center plane CP.

[0033] A pair of pedal units 72 preferably are slideably mounted on the guide rails 68. The pedal units 72 can be made of plastic or metal material. Each pedal unit 72 comprises a footrest 74 and a slider 76. One of the sliders 76 spans the upper and lower guide rails 68 on the port side, while the other slider 76 spans the upper and lower guide rails 68 on the starboard side.

[0034] Each footrest 74 extends laterally and outwardly from each slider 74. Preferably, each top end of the footrests 74 is slightly inclined forwardly so that each foot of the rider can easily and conformably rest thereon. Each footrest 74 can have one or more foot straps (not shown) to fix the foot of the rider more strictly to the footrest 74. Preferably, the position of each pedal unit 72 is adjustable to accept every tread stroke of different riders. The pedal units 72 can slide on the guide rails 68 fore to aft with tread force alternately given to the pedal units 72 by the rider. In operation, the rider sits in the seat unit 46 and alternately gives the tread force to the pedal units 72 so that each pedal unit 72 linearly slides along the guide rails 68. As such, the pedal units 72 can reciprocally move back and forth as indicated with the arrows A of FIGS. 3 and 4. By using the foot straps, a rider can push on one pedal with one foot and simultaneously pull with the other foot and thereby transmit more power to the slide mechanism 56.

[0035] The converting mechanism 58 preferably includes a drive unit 80, an idler unit 82, a one-way transmission 84 and an output shaft 85. The drive unit 80 is located in the rear of the slide mechanism 56, while the idler unit 82 is located in front of the slide mechanism 56. That is, the drive and idler units 80, 82 together interpose the slide mechanism 56 therebetween and are affixed to the frame members 64, 66, respectively, by fasteners such as, for example, bolts and nuts.

[0036] The drive unit 80 has a vertical frame member 86 mounted on the frame member 66 of the slide mechanism 56 on its rear side by the fasteners as shown in FIG. 5. Other horizontal and vertical frame members 88, 90, 92 together form a framework that supports components of the converting mechanism 58. Similarly, the idler unit 82 is mounted on the frame member 64 with another frame member disposed on the front side of the frame member 64.

[0037] With reference to FIG. 5, the illustrated drive unit 80 includes a drive pivot shaft 96 having a vertical axis extending through the center plane CP. The horizontal frame members 88, 90 pivotally journal the pivot shaft 96 with bearings 98, 100. A drive pulley 102 is rigidly fitted onto the pivot shaft 96 and is disposed between the upper and lower horizontal frame members 88, 90.

[0038] With reference to FIG. 3, the idler unit 82, in turn, preferably includes an idler pivot shaft 104 having a vertical axis extending through the center plane CP. Horizontally extending frame members (not shown) pivotally journal the pivot shaft 104 with bearings. An idler pulley 106 is rigidly fitted onto the pivot shaft 104 and is disposed between the horizontal frame members.

[0039] The flexible transmitter 60 preferably is wound around both of the pulleys 102, 106. The illustrated flexible transmitter 60 is a belt having a certain width vertically. Both of the sliders 76 are coupled with the transmitter 60. Optionally, separate belt members can be connected with each of the sliders 76. Because of the arrangement, the flexible transmitter 60 conveys the tread force imposed onto the pedal units 72, to the drive pivot shaft 96. The pivot shaft 96 converts the reciprocal slide movements of the pedal units 72 to pivotal movements thereof that change directions alternately with the reciprocal movements. In other words, the converting mechanism 58 converts the tread force toward the pedal units 72 to pivotal force of the pivot shaft 96.

[0040] The idler unit 82 is not necessarily provided and can be omitted. In this alternative arrangement, part of the flexible transmitter 60 existing forwardly of the pedal units 72 is not necessary.

[0041] With reference to FIG. 5, the one-way transmission 84 preferably is located below the drive unit 80 to connect the pivot shaft 96 to the output shaft 85. The output shaft 85 is journaled for rotation by the vertical frame members 86, 92. In the illustrated arrangement, one forward bearing 110 and two rear bearings 112 support the output shaft 85. The output shaft 85 preferably has a pair of blocks 114 disposed next to the respective bearings 110, 112 to prevent the output shaft 85 from slipping off the frames 86, 92.

[0042] A first bevel gear 118 is rotatably connected to a bottom end of the pivot shaft 96. The second and third bevel gears 120, 122 are rotatably connected to the output shaft 85. More specifically, the second bevel gear 120 is placed forward from the pivot shaft 96 and the third bevel gear 122 is positioned rearwardly from the pivot shaft 96. Both of the second and third bevel gears 120, 122 are meshed with the first bevel gear 118.

[0043] The second bevel gear 120 is connected with the output shaft 85 via a first one-way clutch 124. Thus, when the second bevel gear 120 rotates in a predetermined direction, the clutch 124 engages the output shaft 85 and rotates the shaft 85 in the predetermined direction. The third bevel gear 122 is connected with the output shaft 85 via a second one-way clutch 126. Thus, when the third bevel gear 122 rotates in the predetermined direction, the clutch 126 engages the shaft 85 and rotates the shaft 85 in the predetermined direction.

[0044] For instance, if the pivot shaft 96 pivots in one direction, the first bevel gear 118 pivots in a first pivot direction. Because the second and third bevel gears 120, 122 are both meshed with the first bevel gear 118, they rotate in opposite or reverse directions relative to each other. When the bevel gear 118 rotates the second bevel gear in the predetermined direction, the pivotal force of the pivot shaft 96 is conveyed to the output shaft 85 only through the second bevel gear 120 via the first one-way clutch 124. Conversely, when the pivot shaft 96 pivots in the opposite direction, the first bevel gear 118 rotates the third bevel gear 122 in the predetermined direction and thus, the pivotal force of the pivot shaft 96 now is conveyed to the output shaft 85 only through the third bevel gear 122 via the second one-way clutch 124. As such, the output shaft 85 rotates only in one direction even though the pivot shaft 96 pivots alternately in different directions in accordance with the reciprocal sliding movements of the pedal units 72.

[0045] A single output shaft member can define the output shaft 85 and extend all the way to the rear portion of the hull 32. Alternatively, separate shaft members together define the output shaft 85. FIG. 5 illustrates an exemplary arrangement in part. That is, a hollow shaft member 128 is connected with a solid shaft member 130 to extend the output shaft 85 rearwardly. In any arrangements, the output shaft 85 can extend under the seat unit 46.

[0046] Because the watercraft employs a slide mechanism instead of the conventional rotary-type loading mechanism, the watercraft can be made with a lower profile upper deck. Additionally, the center of gravity of the watercraft 30 with a rider operating the slide mechanism, fluctuates over a smaller vertical range relative to the fluctuations generated by a watercraft employing a rotary-type loading mechanism.

[0047] With reference to FIG. 6, the illustrated watercraft 30 can optionally include a power assist mechanism or auxiliary drive unit 134, although the mechanism 134 is not necessarily provided. With reference still to FIGS. 1 and 2 and additional reference to FIG. 6, the power assist mechanism 134 will be described below.

[0048] The illustrated power assist mechanism 134 is substantially disposed under the backrest 50 thereby contributing to the compactness of the watercraft 30. The illustrated power assist mechanism 134 preferably includes a planetary transmission 136, a motor unit 138, batteries 141 and a clutch device 142.

[0049] The planetary transmission 136 includes a main shaft 144 extending generally horizontally along and on the center plane CP and offset from the output shaft 85 of the manual drive unit 54. A transmission gear 146 disposed at a rear end of the output shaft 85 meshes with another transmission gear 148 disposed at a forward end of the main shaft 144 to connect the output shaft 85 to the main shaft 144. An outer diameter of the gear 148 preferably is larger than an outer diameter of the gear 146, thereby providing a gear reduction set.

[0050] The planetary transmission 136 farther includes a sun gear 152, planet gears 154, a planet carrier 156, a ring gear 158, a resultant force shaft 160 and a large bevel gear 162. The sun gear 152 is journaled for rotation on the main shaft 144. The planet carrier 156 is coupled with the main shaft 144 via a one-way clutch and has a plurality of shafts extending toward locations around the sun gear 152. The planet gears 154 are disposed around the sun gear 152 and are journaled for rotation by the shafts of the planet carrier 156. The planet gears 154 mesh with the sun gear 152.

[0051] A torque sensor arm 163 is affixed to the sun gear. The arm 163 can flex or pivot around the main shaft 144 in proportion to the torque of the tread force given by the rider. A potentiometer or angular position sensor 165 is additionally provided to sense an angular position of the torque sensor arm 163.

[0052] The ring gear 158 surrounds the planet gears 154 and meshes with the respective planet gears 154. The planet gears 154 not only spin about their own axes but also revolve around the sun gear 152. The resultant force shaft 160 is coupled with the ring gear 158 and with the large bevel gear 162. The resultant force shaft 160 also is coupled with a propulsion shaft 164 by a universal joint 166. The foregoing propeller 40 is mounted on an end portion of the propulsion shaft 164.

[0053] The motor unit 138 is placed above or on a lateral side of the planetary transmission 136. The motor unit 138 includes an electric motor and a speed reducer that reduces the rotational speed of the motor. An output shaft of the motor unit 138 is connected with an output bevel gear 168 via the clutch device 140. The output bevel gear 168 meshes with the large bevel gear 162 of the planetary transmission 136. The foregoing one-way clutch of the planet carrier 156 prevents the motor unit 138 from driving the main shaft 144. The rider can selectively connect or disconnect the motor unit 138 with the planetary transmission 136 by operating the clutch device 140. An electric control unit (not shown) is additionally provided to control an output power of the motor unit 138.

[0054] The batteries 141 supply electric power to the motor unit 138 and to the control unit 169. Each battery 141 in the illustrated arrangement generally has the same size and the same weight as one another. The respective batteries 141 preferably are located on both lateral sides of the power assist mechanism 134 and apart from the power assist mechanism 134 with generally the same distance to keep balance of the watercraft 30 in weight. This is because that the batteries 141 are heavy components as well as the power assist mechanism 134. The number of the batteries is changeable. For instance, a single battery can replace the two batteries 141. FIGS. 1 and 2 illustrate the single battery 141 a in phantom as located in front of the manual drive unit 54 on the center plane CP. Of course, the single battery 141 a can be placed, for example, in the rear of the power assist unit 134. Similarly, three or more batteries can be provided in keeping the balance of the watercraft 30 in weight.

[0055] When the rider imparts tread force onto the pedal units 72, the output shaft 85 of the manual drive unit 54 rotates the main shaft 144 of the planetary transmission 136 through the gears 146, 148 so that the main shaft 144 rotates in a speed that is in proportion to movement of the pedal units 72. The main shaft 144 rotates the sun gear 152 which rotates the planet gears 154. Simultaneously, the torque sensor arm 163 flexes or pivots around the main shaft 144. The potentiometer 165 senses the angular position or flexation of the arm 163 and sends a signal to the control unit 169.

[0056] The control unit 169 controls the output power of the motor unit 138 in response to the signal from the potentiometer 165. More specifically, the control unit 169 controls the motor unit 138 so that the rotational speed of the motor changes in accordance with a preset assist ratio relative to the sensed torque and the built-in speed reducer connected to the motor and thereby outputs power in a reduced speed. In one alternative, the control unit can have a changeable assist ratio in response to various conditions. If the clutch device 140 connects the motor unit 138 to the output bevel gear 168, the output power from the motor unit 138 is added to the tread force provided by the rider. The resultant force is transmitted from the resultant force shaft 160 to the propulsion shaft 164 via the universal joint 166. The propeller 40 thus is rotated to propel the watercraft 30 forwardly.

[0057] The rider can cut off the assist power from the motor unit 138 by disconnecting the clutch device 140. Under this condition, the watercraft 30 is propelled only by the tread force given by the rider. On the other hand, the rider can entirely utilize the power from the motor unit 138. Under this condition, the watercraft 30 is propelled only by the power from the motor unit 138 and the rider is released from treading the pedal units 72.

[0058] Similar power assist mechanisms are disclosed in, for example, U.S. Pat. Nos. 5,226,501, 5,375,676, 5,570,752 and 5,664,636 and also Japanese Laid Open Publication No. 7-156880 (published on Jun. 20, 1995), the disclosures of which are hereby incorporated by reference.

[0059] With reference to FIGS. 1 and 2 as well as FIGS. 7-9, the retractable sponsons 44 and the linkage mechanism connecting the sponsons 44 to the hull 32 are described below in greater detail.

[0060] The respective sponsons 44 are buoyant and preferably are made of the same material of the hull 32, such as, for example, a molded fiberglass reinforced resin or a sheet molding compound. Each sponson 44 is connected to a lower rear surface of the lower hull section 32 b by a pair of link arms 174. Appropriate fasteners including, for example, bolts and nuts are available to pivotally affix the link arms 174 to the lower hull section 32 b and the sponsons 44.

[0061] The sponsons 44 preferably are completely located under the hull 32 when the sponsons 44 are in the fully retracted position. The fully retracted position is indicated by the phantom line 176 in FIG. 7. Because the watercraft 30 is narrow when the sponsons 44 are retracted, the rider can achieve higher speeds. With the sponsons 44 deployed in the fully extended position, the watercraft 30 achieves greater stability, which is particularly useful during docking manuevers, or when the rider wants to rest. In particular, if the rider reclines the backrest 50 to the fully reclined position, the rider can rest more safely with the sponsons in the fully extended position.

[0062] The rider may use a paddle 178 to propel the watercraft 30. Preferably, the sponsons 44 are arranged such that, in the fully extended position, the sponsons 44 are beyond the moving limits 180 of the paddle 178. Typically, the paddle 178 has a length of 2.0-2.2 meters. The arrangement and configuration of the sponsons 44 should be determined in light of the length of an associated paddle.

[0063] The sponsons 44 can protect the propeller 40 when the watercraft 30 is operated in shallow water. The propeller 40 is further protected by the arrangement shown in FIG. 8. A line 184 extending horizontally from a bottom end of each sponson 44 is advantageously positioned lower than another line 186 extending horizontally from an axis of the propulsion shaft 164, i.e., a center of the propeller 40. The watercraft 30 can proceed through shallow water with the propeller 40 arranged horizontally. The rider can use the paddle 178 in this situation to propel the watercraft 30. The arrangement also is advantageous when the watercraft 30 is placed on the beach, on a pedestal, a rack, or the like. Alternatively, the sponsons 44 can be elongated vertically so that the bottom ends of the sponsons 44 are positioned lower than a line 188 of FIG. 8 that extends from one edge of the propeller 40 that is placed at the bottom. In this alternative arrangement, the watercraft 30 can proceed through shallow water using the propeller 40 rather than the paddle 178 and can more safely be laid on any surface regardless of the angular position of the propeller 40.

[0064] A separate carrier for containing tools or other items can be attached, for example, on the hutch 38 as shown in FIG. 7. The illustrated hutch 38 has four hooks 192 to fix such a carrier.

[0065] The hull and the sponsons can take any configuration. For instance, FIG. 10 schematically illustrates another hull configuration. The hull 32 in this configuration is divided on the center plane CP into a port side hull section 32 c and a starboard side hull section 32 d. Both of the hull sections 32 c, 32 d are coupled together to form the single hull 32.

[0066]FIG. 11 illustrates another combination of the hull 32 with the sponsons 144. Both lateral sides of the hull 32 are left blunt. The sponsons 144 nest with the blunt portions, as shown in FIG. 11.

[0067] Of course, the foregoing description is that of a preferred construction having certain features, aspects and advantages in accordance with the present invention. Various changes and modifications may be made to the above-described arrangements without departing from the spirit and scope of the invention, as defined by the appended claims. For instance, two or more seat units and manual drive units can be provided. All the tread force of the riders is combined together by, for example, connecting the flexible transmitters. Also, other types of the propeller are available. For example, a fin type propeller can replace the rotational type propeller. The fin can be arranged to sway with the movement of the slide movement of the pedal units. Accordingly, the scope of the present invention should not be limited to the illustrated configurations, but should only be limited to a fair construction of the claims that follow and any equivalents of the claims. 

What is claimed is:
 1. A watercraft comprising a buoyant hull, a seat unit mounted on the hull, a propulsion device arranged to propel the hull, and a manually operated apparatus arranged to power the propulsion device, the manually operated apparatus being disposed in front of the seat unit and comprising a slide mechanism including a pair of slideable pedals.
 2. The watercraft as set forth in claim 1, wherein the propulsion device includes a rotatable member, the manually operated apparatus additionally comprising a converting mechanism arranged to convert a sliding movement of the pedals to a rotational movement of the rotatable member.
 3. The watercraft as set forth in claim 2, wherein the converting mechanism includes an output shaft extending rearwardly, the propulsion device includes a propulsion shaft on which the rotatable member is mounted, both the output shaft and the propulsion shaft are coupled together in the rear of the seat unit.
 4. The watercraft as set forth in claim 2 additionally comprising a power assist unit, the converting mechanism including an output shaft extending rearwardly, the propulsion device including a propulsion shaft on which the rotatable member is mounted, the power assist unit being interposed between the output shaft and the propulsion shaft.
 5. The watercraft as set forth in claim 4, wherein the power assist unit includes an electric motor, and a planetary transmission arranged to join a power of the electric motor to an output power of the converting mechanism.
 6. The watercraft as set forth in claim 5, wherein the power assist unit additionally includes a clutch to either connect or disconnect the power of the electric motor with the output power of the converting mechanism.
 7. The watercraft as set forth in claim 5, wherein the power assist mechanism is disposed in the rear of the seat unit.
 8. The watercraft as set forth in claim 4 additionally comprising at least one battery to supply electric power to the motor, the battery being disposed next to the power assist unit.
 9. The watercraft as set forth in claim 8, wherein the battery is disposed on a lateral side of the power assist unit.
 10. The watercraft as set forth in claim 4 additionally comprising at least two batteries to supply electric power to the motor, the power assist unit being disposed on a center plane of the hull extending fore to aft perpendicularly, each one of the batteries being disposed on each lateral side of the power assist unit.
 11. The watercraft as set forth in claim 4 additionally comprising at least one battery to supply electric power to the motor, and both the power assist unit and the battery are disposed on a center plane of the hull extending fore to aft perpendicularly.
 12. The watercraft as set forth in claim 2, wherein the slide mechanism includes a pair of guide rails extending fore to aft of the hull and generally in parallel to each other, the pedals being slideable back and forth along the guide rails.
 13. The watercraft as set forth in claim 12, wherein the converting mechanism includes an output shaft and a pivot shaft connected to the output shaft, the manually operated apparatus additionally including a flexible transmitter coupled with both of the pedals and with the pivot shaft so that the pivot shaft pivots along with the sliding movement of the pedals.
 14. The watercraft as set forth in claim 13, wherein the converting mechanism additionally includes a one-way transmission arranged to couple the pivot shaft with the output shaft.
 15. The watercraft as set forth in claim 14, wherein the one-way transmission includes a combination of bevel gears with the pivot shaft and the output shaft, and a clutch unit disposed between the bevel gears and the output shaft.
 16. The watercraft as set forth in claim 12, wherein the converting mechanism includes an output shaft, and first and second pivot shafts interposing the slide mechanism therebetween, the manually operated apparatus additionally includes an endless flexible transmitter coupled with both of the pedals and wound around both of the first and second pivot shafts so that the first pivot shaft pivots with the slide movement of the pedals, the first pivot shaft being connected to the output shaft.
 17. The watercraft as set forth in claim 1, wherein the slide mechanism includes a pair of guide rails extending fore to aft of the hull and generally in parallel to each other, the pedals being slideable back and forth along the guide rails.
 18. The watercraft as set forth in claim 1 additionally comprising at least one sponson linked with the hull, the sponson being moveable between a fully retracted position and a fully extended position.
 19. The watercraft as set forth in claim 1, wherein the seat unit includes a backrest, and a top end of the backrest is generally positioned lower than an uppermost surface of an upper deck of the hull.
 20. The watercraft as set forth in claim 1, wherein a location of the seat unit is adjustable between a fully forward position and a fully rearward position.
 21. The watercraft as set forth in claim 1, wherein the hull has a configuration elongated along a center plane extending fore to aft perpendicularly, the slide mechanism extends generally in parallel to the center plane, and each one of the pedals is separated from one another by the center plane.
 22. A watercraft comprising a hull elongated along a center plane extending fore to aft perpendicularly, a propulsion shaft journaled for rotation in the rear of the hull and extending generally on the center plane, a propeller disposed at the end of the propulsion shaft, and a manual drive unit disposed within the hull and configured to convert linear tread force to rotational force that rotates the propulsion shaft.
 23. The watercraft as set forth in claim 22, wherein the manual drive unit includes a pair of pedals slideably disposed along the center plane so that a rider can alternately push each one of the pedals with the rider's feet.
 24. The watercraft as set forth in 23, wherein the manual drive unit additionally includes a pair of guide rails extending generally in parallel to the center plane, and the pedals slide along the guide rails.
 25. The watercraft as set forth in claim 23, wherein the manual drive unit additionally includes an output shaft connected to the propulsion shaft, a pivot shaft connected to the output shaft, a flexible transmitter coupled with both of the pedals and with the pivot shaft so that the pivot shaft pivots with the sliding movement of the pedals.
 26. The watercraft as set forth in claim 25, wherein the manual drive unit further includes a one-way transmission arranged to couple the pivot shaft with the output shaft.
 27. The watercraft as set forth in claim 22 additionally comprising an auxiliary drive unit configured to add additional rotational force to the propulsion shaft.
 28. The watercraft as set forth in claim 27, wherein the auxiliary drive unit includes an electric motor, and a planetary transmission configured to add rotational force of the electric motor to the rotational force of the manual drive unit.
 29. The watercraft as set forth in claim 22 additionally comprising at least one sponson linked with the hull, the sponson being moveable between a fully retracted position and a fully expanded position. 